1. Technical Field
The present invention relates to an optical system and a laser induced thermal imaging (LITI) apparatus including the same and, more particularly, to an optical system having an image direction modulator and an LITI apparatus including the system.
2. Related Art
Presently, the flat panel display (FPD) is on the rise as a display that replaces the cathode-ray tube (CRT) display because the FPD is lightweight and ultrathin. Typical examples of the FPD are a liquid crystal display (LCD) and an organic light emitting display (OLED). In comparison with the LCD, the OLED has high brightness and a wide viewing angle, and is easily implemented as an ultra-thin display because it needs no backlight.
Such an FPD includes red (R), green (G), and blue (B) pixels to realize full color. Specifically, the LCD includes R, G, and B color filters to realize full color, whereas the OLED includes R, G, and B emission layers to realize full color.
In the OLED, the R, G, and B emission layers may be formed by a laser induced thermal imaging (LITI) method. The LITI method enables fine patterning of the emission layers compared to a deposition method using a shadow mask. Also, the LITI method is advantageously a dry process, unlike an inkjet printing method.
The LITI method requires a donor film including a base film, a light-to-heat conversion (LTHC) layer, and a transfer layer. Thus, laser beams are irradiated onto the base film of the donor film so that the transfer layer is transferred onto an acceptor substrate to form an emission layer pattern. In this case, the emission layer pattern may have a stripe shape. The stripe-shaped emission layer pattern may be obtained by scanning laser beams onto the base film in a lengthwise direction relative to the emission layer pattern. In this case, the laser beams irradiated on the base film have an image which is fixed around an X-axis or Y-axis depending on the type of LITI apparatus. The lengthwise direction of the emission layer pattern depends on a direction of the image of the laser beams.
Meanwhile, whether the lengthwise direction of the emission layer pattern should be parallel to the X-axis or the Y-axis direction is determined according to the type of OLED. Accordingly, there is a problem in that a certain type of LITI apparatus must be used according to the lengthwise direction of the emission layer pattern.